1. Field of the Invention
The present invention relates generally to audio processing, and more particularly to controlling adaptivity of noise reduction in an audio signal.
2. Description of Related Art
Noise reduction systems in audio devices utilizing two or more microphones typically use spatial cues to reduce noise. The spatial cues may be determined between acoustic signals received at the two or more microphones to help distinguish sources of desired signals such as speech from undesired signals such as noise.
The spatial cues can be used to derive relative physical locations of the sources, which can further help distinguish between speech and noise sources. For example, spatial constraints may be imposed using a classification threshold. Any source within a target region, which includes a reference point indicating a nominal usage position for the device, is classified as a speech source, and any source outside the target location is classified as a noise source. This allows the device to be positioned or moved slightly away from the nominal usage position during usage, whilst still rejecting most signals arising from noise sources (i.e. the signals arising from noise sources outside the target region) and simultaneously preserving signals arising from within the target region such as a desired speech source.
It is desirable to provide noise reduction techniques which can improve speech quality by optimizing robustness.